Individuals with schizophrenia have an increased risk of developing dementia, according to a population-based cohort study of more than 2.8 million people over age 50. The risk was especially seen in those younger than 65.
Participants, aged 50 and older, were from 6 registers, and 20,683 had schizophrenia. Investigators looked at incidence rate ratios (IRR) and cumulative incidence of proportions (CIP) over an 18-year period.
136,012 of the subjects—including 944 with schizophrenia— developed dementia. Those with schizophrenia were more than twice as likely to develop dementia. This remained the case even after adjusting for medical comorbidities. After adjusting for substance abuse, those with schizophrenia were still 1.71 times as likely to develop dementia vs those without the condition.
The IRR was higher in those:
• younger than 65: 3.77
• who were male: 2.38
• with a partner: 3.16
• without cerebrovascular disease: 2.23
• who were not substance abusers: 1.96
The CIPs of developing dementia for those with and without schizophrenia were:
• 1.8% and 0.6%, respectively by age 65
• 7.4% and 5.8%, respectively by age 80
Citation: Riisgaard A, Munk T, Charles M, et al. Long-term risk of dementia in persons with schizophrenia: A Danish population-based cohort study. JAMA Psychiatry. 2015; October 7, 2015. doi:10.1001/jamapsychiatry.2015.1546.